Electronic modules frequently include a circuit carrier carrying one or more electronic components, e.g. one or more semiconductor chips, each having an integrated semiconductor switch. For instance, such an electronic module may include an inverter, a power supply for supplying an inductive load like a motor, or any other power electronic circuit. The circuit carrier serves to carry and electrically interconnect the electronic components. In order to dissipate heat produced by power losses in the electronic components, or, more generally, in an electronic circuit realized on the circuit carrier, the electronic module may be pressed against a heat sink. An exterior heat exchange surface of the module with a layer of thermal interface material (e.g. a thermal grease, phase change materials etc.) is disposed between the heat sink and the module's heat exchange surface so that a significant part of the heat can flow from the electronic components via the circuit carrier and the layer of thermal interface material towards the heat sink.
The thermal interface material serves to eliminate large air gaps or other gas-filled voids (which act as thermal insulator) from the interface area between the heat exchange surface and the heat sink so as to maximize the heat transfer. The thermal conductivity of conventional thermal interface material (e.g. from 0.4 W/(m·K) to 1 W/(m·K) at a temperature of 25° C.) is greater than the thermal conductivity of the air/gas in the gas-filled spaces, but poor compared to the thermal conductivity of conventional heat sinks. For instance, many conventional heat sinks are produced from aluminum or an aluminum alloy and have, depending on the purity or alloy composition, a thermal conductivity of up to 236 W/(m·K). Therefore, it is desirable to keep the layer of thermal interface material as thin as possible.
However, a real heat exchange surface is uneven or becomes uneven during the assembly of the electronic module so that one or more “remote” sections of the heat exchange surface are disposed more distant from the heat sink than other sections. Irrespective of whether or not the space between the heat sink and a remote section is filled with thermal interface material or not, the comparatively large distance between the remote section and the heat sink increases the thermal transition resistance between the heat exchange surface and the heat sink.
Hence, there is a general need for an electronic module assembly that allows for a low thickness of a thermal interface material between an electronic module and a heatsink.